The invention relates to a tape cassette case.
A length of magnetic tape contained in a tape cassette has its opposite ends anchored to a pair of hubs which are rotatably disposed within the cassette, and is wound on respective hubs. Because both hubs are rotatable relative to the cassette, there is no means in the cassette itself which prevent an unreeling of the magnetic tape. To accommodate this problem, it has been the practice heretofore to provide the cassette case with locking means engaging both hubs to prevent their rotation at least when the cassette is received in the case, thus preventing the unreeling of the tape.
A typical example of the prior art will be described with reference to FIGS. 1 to 3. There is shown a tape cassette case 1 including a box portion 2 and a cover portion 3 which is joined with the box portion by means of a hinge 4. All of these portions are integrally molded from vinyl resin, unsaturated polyester resin or the like. In regions 4a, 4b (see FIG. 3) of the boundary with the box portion 2 and the cover portion 3, the hinge 4 has a reduced thickness to facilitate the folding operation, but there still remains sufficient resilience in the material of the hinge to urge the cover portion 3 away from the box portion 2.
A pair of locking members 5a, 5b are fixedly mounted and spaced from each other on the central portion of the box portion 2 for preventing the unreeling of the tape by engaging with tape hubs 6a, 6b of a tape cassette 6 when it is received in the case (see FIGS. 2 and 3). When the cassette 6 is received within the box portion 2, as indicated by double dot chain line in FIGS. 2 and 3, the tape hubs 6a, 6b are fitted on the locking members 5a, 5b, which prevent their rotation, and hence the unreeling or slackening of the tape. After the cassette 6 is received in the box portion 2, the cover portion 3 is closed over the box portion 2. The box portion 2 has a sidewall 2a on which a pair of detent tabs 7, 8 are provided, with a stop 9 for the cover portion 3 being provided on the bottom of the sidewall. The cover portion 3 has a corresponding sidewall 3a which is internally formed with a pair of recesses 10, 11 for engagement with the detent tabs 7, 8.
The tape cassette 6 is received in the case 1 thus formed, as illustrated in FIG. 2. As is well recognized, the tape hubs 6a, 6b of the cassette 6 are disposed symmetrically with respect to the crosswise centerline thereof and are rotatable in a pair of through-openings 14a, 14b formed through the opposite major faces of the cassette. The hubs 6a, 6b are each adapted to receive a drive shaft (not shown) of a tape recorder. A length of magnetic tape Tp has its opposite ends anchored to the hubs 6a, 6b and is wound thereon. Specifically, a length of tape extends from one of the hubs around a pair of diverting rollers 15a, 15b to the other hub, thus being held taut along the front edge face of the cassette.
When the cassette 6 is received in the case 1, the locking members 5a, 5b provided on the bottom wall of the case 1 are fitted into center openings in the hubs 6a, 6b and engage between tabs 6a', 6b'which extend radially inward from the wall of the openings, whereby the rotation of the hubs is prevented. Thus, it will be seen that the tape Tp will be held taut and no slackening thereof will occur if the locking members 5a, 5b can be engaged with the tape hubs 6a, 6b under the condition that the hub 6a is sufficiently rotated in the direction of an arrow A to maintain the tape taut. However, in the conventional arrangement, there is a certain amount of tolerance between the tabs 6a', 6b' and the locking members 5a, 5b to permit a rattling of the latter, and this makes it difficult, if not impossible, to maintain the tape taut in the presence of vibrations which may be caused during the shipment. On the other hand, if the tape is slackened before the cassette is inserted into the case, there is provided no means in the prior art arrangement which can be utilized to eliminate the slackening. As a consequence, the tape Tp remains slack, which may cause a twisting or folding of the tape to degrade its performance.
It will also be seen that the cassette 6 itself is not capable of preventing the rotation of the tape hubs, so that when it is removed from a tape recorder (not shown), the hubs are free to rotate, thus immediately causing an unreeling or slackening of the tape. Hence, it will be desirable to use a sharp member such as pencil or the like to rotate the hubs to achieve a taut condition of the magnetic tape when inserting the cassette 6 into the case 1. However, this requires some tool, and if the hubs are rotated in a wrong direction, a further slackening of the tape will result. It will thus be seen that the use of fixed locking members cannot achieve a slack-free tape condition when the cassette is received in the case or cannot correct any slackening of the tape.